Scheduling of delay-sensitive traffic

ABSTRACT

Uplink traffic control device, method and computer program product to determine that predictive scheduling is to be applied for the mobile station. Thereafter an uplink transmission scheme is determined for the predictive scheduling. Thereafter, periodic messages comprising uplink transmission grants, according to the uplink transmission scheme, are sent to the mobile station, the messages further comprising a request for a downlink channel quality indicator (CQI) report.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/044,468, filed Jul. 24, 2018, which is a continuation of U.S.application Ser. No. 15/193,002, filed Jun. 24, 2016, issued as U.S.Pat. No. 10,064,207 on Aug. 28, 2018, which is a continuation of U.S.application Ser. No. 14/360,592, filed May 23, 2014, issued as U.S. Pat.No. 9,380,603 on Jun. 28, 2016, which is the National stage ofInternational Application No. PCT/SE2011/051491, filed Dec. 9, 2011,which are all hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to predictive scheduling in wirelesscommunication networks.

BACKGROUND

In the 3rd Generation Partnership Project (3GPP) standardization bodytechnologies like Global System for Mobile Communication (GSM),High-Speed Packet Access (HSPA) and Long Term Evolution (LTE) have beenand are currently developed.

LTE is the latest technology standardised. It uses an access technologybased on OFDM (Orthogonal Frequency Division Multiplexing) for thedownlink (DL) and Single Carrier FDMA (SC-FDMA) for the uplink (UL). Theresource allocation to mobile stations, in LTE denoted user equipment(UE), on both DL and UL is performed adaptively by the concept of fastscheduling, taking into account the instantaneous traffic pattern andradio propagation characteristics of each mobile station. Assigningresources in both DL and UL is performed in a so-called schedulersituated in a base station, in LTE often denoted eNodeB.

In e.g. LTE, uplink transmissions are scheduled by a base station. Agrant is transmitted on the downlink control channel PDCCH and themobile station responds with a transmission using the resourcesspecified in the grant and with the size specified in the grant. Themobile station can let the base station know that it wants to transmitby sending a scheduling request (SR) on the uplink control channel PUCCHat predefined times. Typically, the mobile station transmits an SR whichis followed by one or many grants, each resulting in one uplinktransmission. This is commonly referred to as dynamic scheduling.

With the higher speeds a number of various applications that a user ofthe mobile station can be engaged in have evolved. It is for instance ofinterest for a user to involve him- or herself in online games, wheresmall amounts of uplink data are transferred fairly often from themobile station to another device involved in a game. Here thetransferred data may be gaming commands and the other device may beanother mobile station or another type of user terminal like a PC oreven a server. Gaming is one example of delay-sensitive traffic. Theincrease of this delay-sensitive traffic and its significant share inthe internet traffic leads to the radio interfaces of wirelesscommunication systems having to meet various latency requirements toensure that a mobile station user can enjoy the activities employingthis type of traffic. Another example of delay-sensitive traffic isping. Ping is for instance used to estimate the delay of a channel aswell as to measure the performance in radio systems in order to forinstance compare and/or rank different systems.

Setting up of traffic in a wireless communication network is oftenreferred as allocation of resources. When resources are allocated to amobile station desiring to send data in the uplink, there are normally anumber of activities that have to be performed. First the mobile stationsends a scheduling request (SR). This is followed by the base stationresponding with a grant, which grant includes information on whattime/frequency resources the mobile station shall use. The mobilestation then transfers a Buffer Status Report (BSR) after which the basestation issues a grant for further data. It is not until it receivesthis further grant that the mobile station can transmit the actual datait intends. This process is time consuming, especially if the mobilestation is to run through the process each time it desires to transferdata.

It is not required that an SR precedes the grant. When the base stationknows that a mobile has a periodic service or for some other reason canpredict future data arrivals it can transmit a grant to the mobilewithout waiting for an SR. It is also possible to blindly transmitgrants in order to speed up the scheduling. These scheduling methods arecalled predictive scheduling.

However, predictive scheduling may cause so called padding transmissionsfrom a mobile station if the mobile does not have data in the buffer.Padding transmissions are messages containing no relevant information,and should thus be avoided as much as possible.

There is in view of what has been described above a need for avoidingthe sending of transmissions comprising only padding for a mobilestation provided with predictive scheduling.

SUMMARY

One object of the present disclosure is therefore directed towardsavoiding the sending of transmissions comprising only padding for amobile station provided with predictive scheduling.

The above mentioned object is according to a first aspect achievedthrough a method performed in a node of a wireless communication networkcomprising a mobile station and a base station. The method comprisesdetermining that predictive scheduling is to be applied for the mobilestation, whereby an uplink transmission scheme is determined for thepredictive scheduling. Thereafter periodic messages comprising uplinktransmission grants, according to the uplink transmission scheme, aresent to the mobile station, said messages further comprising a requestfor a downlink channel quality indicator, CQI, report.

The above mentioned object is according to a second aspect achieved byan uplink traffic control device in a wireless communication networkcomprising a mobile station and a base station. The uplink trafficcontrol device comprises an uplink scheme determining unit configured todetermine that predictive scheduling is to be applied for the mobilestation and to determine an uplink transmission scheme for thepredictive scheduling. The uplink traffic control device furthercomprises a transmission control unit configured to send periodicmessages comprising uplink transmission grants, according to the uplinktransmission scheme, to the mobile station, said periodic messagesfurther comprising a request for a downlink channel quality indicator,CQI.

The above mentioned object is according to a third aspect also achievedthrough a computer program for use in a wireless communication networkcomprising a mobile station and a base station. The computer programproduct comprises a computer readable storage medium comprising computerprogram code causing an uplink scheme determining module of an uplinktraffic control device to:

determine that predictive scheduling is to be applied for the mobilestation

determine an uplink transmission scheme for the predictive scheduling,and send periodic messages comprising uplink transmission grants,according to the uplink transmission scheme, to the mobile station, saidmessages further comprising a request for a downlink channel qualityindicator, CQI, report.

The above mentioned aspects enables the predictive schedulingtransmissions from the mobile station to comprise useful information,since the mobile station is requested to send a CQI report upon receiptof the uplink transmission grant. This means that uplink transmissionsgenerated in response to the predictive scheduling will at leastcomprise a CQI report and thus these uplink transmissions will not onlycomprise padding.

It should be emphasized that the term “comprises/comprising” when usedin this specification is taken to specify the presence of statedfeatures, integers, steps or components, but does not preclude thepresence or addition of one or more other features, integers, steps,components or groups thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will now be described in more detail in relationto the enclosed drawings, in which:

FIG. 1 schematically shows a mobile station communicating with a firstbase station in a wireless communication network, where the network alsocomprises a second base station and two further nodes;

FIG. 2 shows a simplified block schematic of an uplink traffic controldevice;

FIG. 3 schematically shows scheduling requests sent by the mobilestation to the first base station together with grants sent as responsesas well as additional grants;

FIG. 4 shows a flow chart of a number of method steps in a generalmethod for scheduling uplink traffic according to an embodiment;

FIG. 5 schematically shows a flow chart of method steps for preparinguplink transmission grants;

FIG. 6 schematically shows a flow chart of a number of method steps in amethod for scheduling uplink traffic according to an embodiment;

FIG. 7 schematically shows a flow chart of a number of method steps in amethod for controlling predictive scheduling;

FIGS. 8 and 9 schematically shows the sending of messages between amobile station and a base station;

FIG. 10 illustrates a diagram showing an example of how the energyconsumption varies for a mobile station based on a reference trafficmodel; and

FIG. 11 schematically shows a computer program product in the form of aCD ROM disc with a computer program performing the functionality of thesolution according to the present disclosure.

DETAILED DESCRIPTION

In the following description, for purposes of explanation and notlimitation, specific details are set forth such as particulararchitectures, interfaces, techniques, etc. in order to provide athorough understanding of the invention. However, it will be apparent tothose skilled in the art that the solution according to the presentdisclosure may be practiced in other embodiments that depart from thesespecific details. In other instances, detailed descriptions ofwell-known devices, circuits and methods are omitted so as not toobscure the description of the invention with unnecessary detail.

Parts of the disclosure is generally directed towards reducing thepadding transmissions from a mobile station when provided withpredictive scheduling, e.g. when involved in delay-sensitive activitiessuch as on-line gaming or ping.

A non-limiting example context of a wireless communication network 10will now be described in more with reference to FIG. 1. The wirelesscommunication network 10 may here be a cellular network such as aUniversal Mobile Telecommunications System (UMTS) network or a Long TermEvolution (LTE) network. These are merely some examples of some types ofnetworks in which the invention may be implemented. Several other typesof networks exist.

To the network 10 there is connected a mobile station 10 beingassociated with a user. Here the mobile station may be a phone, such asmobile phone or a computer like a lap top computer or a palm topcomputer. These are just a few examples of mobile stations that can beused. A mobile station is in LTE often denoted User Equipment (UE).

The mobile station 20 is more particularly communicating with a firstbase station BS 12. The first base station 12 is here one network node.The system also includes a number of other network nodes, where as anexample a second base station BS 14 is shown as well as two more centralnodes, a Proxy Call Session Control Function P-CSCF server 16 and aServing Call Session Control Function S-CSCF 18. These latter nodes arenodes at a higher hierarchical level of the system than the basestations. For this reason, the base stations 12 and 14 are oftendescribed as being provided in an access network of the wirelesscommunication network, while the servers 16 and 18 are described asprovided in a core network of the wireless communication network.

FIG. 2 shows a block schematic of an uplink traffic control device 21.In one variation this traffic control device 21 is the first basestation. However, it should be realized that it may as an alternative beprovided as another network node. If for instance the wirelesscommunication network is an UMTS network, then the device can beprovided as a radio network controller (RNC). As yet anotheralternative, it is possible that the device 21 is provided in a node ona higher hierarchical level, such as in a server in the core network,for instance the S-CSCF 18.

The uplink traffic control device 21 does in this example comprise atleast one antenna 34 and here only one antenna is shown, which antennais connected to a radio circuit RA 36. A data modulator DM 38 is in turnconnected to the radio circuit 36. The uplink traffic control device 21also comprises an uplink scheme determining module USDM 22. The uplinkscheme determining module 22 in turn comprises a number of units. Itcomprises a transmission control unit TCU 30, which is connected to thedata modulator 38. The transmission control unit TCU 30 is connected toa scheme application control unit SACU 32 and to an input buffer 31,which buffer 31 is also connected to an uplink scheme determining unitUSDU 24. The uplink scheme determining unit 24 is in turn connected to atransmission requirement estimating unit TREU 26, to an energyconsumption estimating unit ECEU 28 and to the scheme applicationcontrol unit 32. The transmission control unit TCU 30 is in this examplea so-called scheduler, which is responsible for scheduling uplink datain the time and/or frequency domain for a number of mobile stationsbeing connected to the communication network via the uplink trafficcontrol device.

In LTE the downlink will support channel dependent scheduling in boththe time and frequency domains. The radio base station will transmitreference signals that the mobile stations use to determine the downlinkchannel quality. The mobile stations will send Channel QualityIndication (CQI) reports back to the base station that are used by ascheduler located in the base station for scheduling traffic within thecell that the base station serves.

In the LTE network the mobile station is specified to be able totransmit different types of CQI reports. For example, the mobile willhave the capability to transmit full CQI reports and partial CQIreports. Full CQI report covers the whole downlink transmissionbandwidth but they may have different frequency resolution. The CQIreports may be filtered and processed in different ways, and they may beencoded in different ways, see also 3GPP TS 36.213 V8.2.0. “Physicallayer procedures”.

The mobile station 20 is typically equipped with an uplink buffer andwhen there is data in this buffer needed to be transmitted, the mobilestation transmits a scheduling request SR to the wireless communicationnetwork 10 and more particularly to the first base station 12. Such ascheduling request is in LTE typically transmitted on a dedicated SRchannel (D-SR) or on a contention based Random Access Channel (RA-SR). AD-SR requires that the mobile station is synchronized in the uplink (UL)and that the mobile station has been assigned an SR channel on thePhysical Uplink Control Channel (PUCCH).

In predictive scheduling a mobile station receives transmission grantswithout actual knowledge of the mobile station buffer content.

The data transmission requirements of the mobile station can then beestimated. It is here possible to monitor the behaviour of the mobilestation and use obtained statistics to control the amount of data andthe periodicity of the data that the base station is to receive from themobile station.

FIG. 3 schematically shows how a mobile station sends schedulingrequests regularly and also how grants are provided as responses to suchscheduling requests. These scheduling requests SR may as an example berepeated every 10-20 ms. It should be realized that in relation to ascheduling request SR all the signals shown in FIG. 3 are in fact beingsent. However, only one grant GR is shown in order to simplify thefigure.

There is thus considerable delay in case the mobile station 20 and basestation 12 are to go through all the above-mentioned steps each time themobile station 20 is about to send data. In order to simplify thesituation and lower the delay, the present disclosure proposes that theuplink traffic control device ensures that some grants are sent despitenon-receipt of scheduling requests. This means that the presentdisclosure proposes that the uplink traffic control device 21, which ina first variation of the invention is the above described first basestation 12, ensures that grants are sent without in fact knowing thatthe mobile station has data in its output buffer intended for thewireless communication system 10 and that the transmission compriseuseful information in form of a CQI report.

How this can be done according to a first embodiment will now bedescribed with reference being made to FIGS. 1, 2 and 4, which latterfigure shows a flow chart of a number method steps in a general methodfor scheduling uplink traffic according to a first embodiment.

The method, which is performed in the network node comprising the uplinktraffic control device 21, starts with the uplink scheme determiningunit 24, determining that predictive scheduling, step 40, is to beapplied for the mobile station. The reasons are depending on a receivedservice indicator associated with or concerning the mobile station 20and/or operator preconfigured parameter to use predicted scheduling.Depending on the situation within a cell, an operator can based on sucha parameter determine to apply predictive scheduling for certain usersor mobile stations. A service indicator associated with or concerningthe mobile station 20 may be a Quality of Service parameter like theparameter Quality Class Indicator (QCI) used in LTE. It is an indicatorthat identifies a type of data traffic that the mobile station wants tosend in the uplink or receives in downlink. This indicator may beobtained by the uplink scheme determining unit 24 from the mobilestation 20. As an alternative it is possible that it is obtained fromanother network node, for instance from a server in the core network,such as the S-CSCF 18 or P-CSCF 16. This indicator also provides apriority setting of the communication of the mobile station in relationto a communication session in which the mobile station or rather theuser of the mobile station wishes to engage, which session would theninvolve delay sensitive traffic such as communication in an on-linegaming session or a ping.

The uplink scheme determining unit 24 then determines, step 42, anuplink transmission scheme of the mobile station 20. The scheme ispreferably determined based on the service type indicator or theoperator preconfigured parameter, i.e. based on the reason for applyingpredictive scheduling. For a mobile station for which it has beendecided to apply predictive scheduling, the predictive scheduling can beinitiated, i.e. started (or re-started in case it has been previouslystopped) with the purpose of reducing the delay of uplink or/anddownlink data transmission. Example of uplink initiated predictivescheduling are receipt of data from a mobile station wherein the bufferstatus report indicates an empty buffer and/or an indication that achannel quality metric such as path loss is within a certain interval orbelow a threshold. Examples of downlink initiated predictive schedulingare detecting that a channel quality metric such as path loss is withina certain interval or above a threshold, and/or an indication that thereis data in the downlink buffer. It could also be decided to blindlytransmit scheduling grants, i.e. apply predictive scheduling by e.g. apolicy decision, thus not being downlink or uplink initiated.

The uplink transmission scheme comprises in this situation an intervalbetween sending of consecutive periodic messages comprising an uplinktransmission grant for the mobile station. The interval being dependenton the reason for determining that predictive scheduling is to beapplied. The uplink scheme determining unit 24 prepares a messagecomprising an uplink transmission grant and a request for a downlink CQIreport. A more detailed description of how the message is prepared willbe later described with reference to FIG. 5. The determination accordingto step 42 may involve estimating the size of data to be transmitted andthe frequency with which the data is to be transmitted by the mobilestation. This estimation may be performed through considering also otherdata such as what data sizes and how frequently data with these sizeshave previously been used in earlier sessions involving e.g.delay-sensitive traffic. The scheme may also be adapted according tochannel quality, for example average path gain for the mobile, oraverage gain to interference plus noise ratio (GINR) in the uplinktraffic control device 21 to obtain a good tradeoff between end userdelay and mobile station battery drain. A mobile with good channelquality will be scheduled with shorter interval between sending ofgrants, whereas a mobile with poorer channel quality will be scheduledwith a longer interval. The tradeoff between scheduling latency andbattery consumption is well achieved by adapting the periodicity withthe channel quality. This will be further described with reference toFIG. 10.

It is here also possible to consider the frequency with which schedulingrequests and BSRs have been sent as well as earlier content of these inrelation to earlier communication sessions of the same type. In this wayan uplink transmission scheme specifies the periodicity of the uplinktransmissions as well as the data size. The scheme is furthermoredetermined in advance of the actual uplink grants being given. Thescheme is thus pre-determined before grants are being sent. Thus, thescheme may initially be provided before the mobile station sends ascheduling request.

Thereafter the uplink scheme determining unit 24 informs thetransmission control unit 30 of the scheme, which transmission controlunit 30 goes on and periodically grants transmissions to be made fromthe mobile station 20 according to the scheme, step 44. This may involvethe transmission control unit 30 issuing grants GR to transmissions,which are being issued using the data modulator 38, radio circuit 36 andantenna 34. Here the uplink scheme determining unit may employ thebuffer 31 for informing the transmission control unit 30. However, itshould be realized that it is also possible with a direct command beingissued. The use of the buffer will be described in more detail withreference to FIG. 6. The scheme may also make room for requested grants,i.e. for grants sent as a result of a received schedule request SR orBSR. If the grant for further data sent after receiving such a requestfrom the mobile station coincides with a grant according to the scheme,the grant according to the scheme may be held back.

In step 45 the node receives, in step 45, transmissions sent from themobile station. The transmissions from the mobile station are sent inresponse to the uplink transmission grants sent from the node in step44. Each of the transmissions sent in response to the predictivescheduling uplink transmission grants comprises a downlink channel CQIreport. The information in the CQI report will be used by the node inorder to provide channel estimation for downlink transmission.

In this way it is possible to grant transmissions in addition to thosefor which the mobile station issues a scheduling request SR. As can forinstance be seen in FIG. 3, the uplink traffic control device 21 issuesseveral additional grants GR in addition to the grants GR issued after ascheduling requests SR. These additional grants speed up mobile stationtransmissions to the wireless communication network.

FIG. 5 shows a flow chart that in more detail describes thedetermination of the uplink transmission scheme and the preparation ofthe messages comprising the uplink transmission grant and the CQI reportrequest. In step 42A the reason for applying predictive scheduling tothe mobile station is established by the USDU 24. Based on the reasonfor applying predictive scheduling an interval between sending ofconsecutive periodic messages comprising an uplink transmission grantfor the mobile station is determined. Further, based on the reason forapplying predictive scheduling the amount of data that the mobilestation is allowed to transmit may be determined.

In step 42B, the message comprising the uplink transmission grant and arequest for a downlink CQI report that is to be sent to the mobilestation is prepared by the USDU 24. Step 42B further comprises thesub-step 42B1 in which it is determined whether the mobile station hasdata to transmit or not. If the mobile station has data to transmit, themessage is provided with information regarding the transport block sizethat the scheduling entity, i.e. the mobile station, is requested in thecurrent Transmission Time Interval. The actual resource allocation, i.e.the amount of allowed transmission data for the scheduling entity, isdecided by the uplink traffic control device based on e.g. a priorityweight associated with the entity. A mobile station with non-zero buffersize has a weight of the correspondent uplink data plus an extra CQIreport weight. Thereafter the method moves on to step 44 according toalternative “Yes”. In step 44 the message comprising the UL transmissiongrant including resource allocation and the CQI report request is sentto the mobile station.

If it in step 42B1 was determined that the mobile station does not havedata to transmit, i.e. the buffer status report indicates an emptybuffer, the method moves on to step 42B2, and the buffer 31, accordingto alternative “No”. In case the uplink traffic control device 21 doesnot have information regarding the whether the mobile station has datato transmit or not, the method also moves on to step 42B2 according toalternative “No”. The uplink scheme determining unit 24 provides aninternal special queue of artificial data in the buffer 31 dedicated tothe mobile station 20. This low-priority queue is provided for thedelay-sensitive data associated with the mobile station 20. Since it isfed with artificial data, the low priority queue will match thedelay-sensitive data. The rate at which this buffer 31 is filled, i.e.the rate with which data is placed, and the amount with which it isfilled causes the transmission control unit to periodically transmitgrants to the mobile station 20 according to the scheme. In step 42B2the message is provided with artificial data having an arbitrary size.The value of the arbitrary size of the artificial data can be aparameter set by an operator. The value of arbitrary size should belarge enough to accommodate a packet size of the traffic, which issubject to be delay optimized, plus the overheads added in differentlayers and a buffer status report. The priority weight associated with amobile station with zero buffer size has a weight of only the CQIrequest weight, which is of much lower priority than the normal uplinktraffic data. Thereafter the method moves on to step 44. In step 44 themessage comprising the UL transmission grant including resourceallocation and the CQI report request is sent to the mobile station.

The effect of implementing a scheme, as described with reference toFIGS. 4 and 5, is that the mobile station subject to predictivescheduling will receive scheduling grants when possible without havingany impact on the performance for other scheduling entities. This meansthat in a low load situation, when there are free resources in time andfrequency, the predictive scheduling will order a-periodic CQI reportrequests that will be sent to the mobile station in the form ofpredictive scheduling uplink transmission grants comprising a downlinkCQI report request. In a high load situation, however, the CQIscheduling entity will not be scheduled since data from normal priorityqueues of other mobile stations will be prioritized.

Commonly, an a-periodic CQI report is only requested by a downlinkscheduler and a pre-scheduling grant only triggers a normal uplinktransmission, the method according to the present disclosure combinesthose mechanisms by applying a predictive scheduling scheme to schedulean a-periodic CQI report. With this method, not only the uplinkscheduling delay is improved due to the predictive scheduling, but alsodownlink CQI report is sent more frequently. As a result, fewertransmissions are wasted since no padding transmissions are sent andmore frequent downlink channel quality updates becomes possible.

Now a more specific embodiment will be described with reference beingmade to FIG. 6, which shows a flow chart of a number of method steps ina method for scheduling uplink traffic according to the secondembodiment.

As in the first embodiment the method starts with the uplink schemedetermining unit 24 determining that predictive scheduling shall beapplied, step 46. Based on the reason for the determination, e.g. anobtained service type indicator, the quality of service associated withthe type of communication the mobile station 20 is to be engaged in thedesired communication session can be decided. From this decision it isthen possible to estimate the data transmission requirements of themobile station 20.

As this is done, the scheme application control unit 32 at the same timeobtains traffic load data concerning the traffic load in the wirelesscommunication system, step 48. This data may be data received from acentral node, such as the P-CSCF or the S-CSCF. Such data is thenreceived via a transport network interface (not shown). It may also belocal traffic load data received from the transmission control unit 30based on the scheduling of other traffic, typically associated withother mobile stations. The traffic load data may here furthermoreinclude data of traffic having a higher priority as well as pre-existingtraffic of the same priority. The traffic control unit 30 will typicallyobtain such data in the course of resource allocation via the antenna 34and radio communication unit 36. The traffic load obtained via thetraffic load data is then compared, by the scheme application controlunit, 32, with a corresponding traffic load threshold. If the trafficload is above the threshold, step 50, then the scheme applicationcontrol unit 32 aborts the uplink scheduling, step 68, which may at thisstage involve instructing the uplink scheme determining unit 24 to stopdetermining an uplink schedule. It may also involve instructing thetransmission control unit 30 to disallow any scheduling of traffic fromthe uplink scheme determining unit 24. If however the traffic load isbelow the threshold, step 50, the uplink scheme determining unit 24 isallowed to continue.

Thereafter, the uplink scheme determining unit 24 may instruct thetransmission requirement estimating unit 26 to estimate transmissionrequirements and may also instruct the energy consumption estimatingunit 28 to estimate the battery consumption of the mobile station. Thetransmission requirement estimating unit 26 may then estimate thetransmission requirements of the mobile station 20, step 52. This may bedone through investigating the service type indicator, which defines thekind of service requested. The indication therefore gives a hint aboutthe requirements of the mobile station 20. The indicator may alsoprovide an initialisation value of the amount of data required. Thetransmission requirement estimating unit 26 may also considerstatistical data regarding the behaviour of the mobile station 20, suchas periodicity and data amounts in previous sessions of the same and/ordifferent types. It is here also possible to consider the fact if thereis any downlink data intended for the mobile station in the session inquestion. At the same time the energy consumption estimating unit 28 mayestimate the battery consumption of the mobile station, step 54. Thismay be based on a model of the energy consumption, the estimatedtransmission requirements and an estimation of the length of thesession. This session length estimation may consider the length ofprevious sessions of the same type. In the battery consumptionestimation, it is furthermore possible to also consider the statisticalgeneral behaviour of the mobile station, such as the frequency andlength of other types of communication sessions. It may also considerdownlink data intended for the mobile station 20.

These estimations are then sent to the uplink scheme determining unit24, which goes on and determines the periodicity of grants and data sizeallowed at each grant, step 56. The determination may thus be based onthe estimated transmission requirements and the estimated batteryconsumption. Typically, the periodicity and size may be determined as atradeoff between the transmission requirements and battery consumptionrequirements. When the uplink scheme determining unit 24 has determineda scheme, it then informs the transmission control unit 30 of the schemeand therefore the transmission control unit 30 periodically schedulesgrants to the mobile station using the data modulator 38, radio circuit36 and antenna 34.

The informing could be provided through sending a direct instruction tothe transmission control unit 30. However, according to the secondembodiment another method is used. Here the uplink scheme determiningunit 24 provides an internal special queue of artificial data in thebuffer 31 dedicated to the mobile station 20. This low-priority queue isprovided for the delay-sensitive data associated with the mobile station20. Since it is fed with artificial data, the low priority queue willmatch the delay-sensitive data. The rate at which this buffer 31 isfilled, i.e. the rate with which data is placed, and the amount withwhich it is filled causes the transmission control unit to periodicallytransmit grants to the mobile station 20 according to the scheme.

The transmission control unit 30 may handle a number of ordinarytransmission control queues for mobile stations, which queues havehigher priority data to be transmitted, such as voice and video data,while the queue in the buffer 31 concerns low priority queue associatedwith the delay sensitive data of the mobile station 20. The uplinkscheme determining unit 24 can therefore be considered to add one extrapriority queue, which is set up with a lower priority than the normalqueues.

As grants are caused to be transmitted in this way, the uplink schemedetermining unit 24 investigates if there is new data received from themobile station 20, such as SR, BSR or real uplink data sent afterreceiving a grant, such as number of received bits or a received CQIreport. This means that at least some of the received data is receivedas a response to the granting of transmissions. If there is such data,step 60, it or information of it is provided to the transmissionrequirement estimating unit 26, which updates the transmissionrequirements. The update can here be based on the number of bitsreceived. It is also possible to consider if any downlink data isintended for the mobile station 20. The information in a received CQIreport will however not affect the scheme but will instead be used fordownlink channel estimation. The energy consumption estimating unit 28may here also update the estimated battery consumption based on thisdata and the elapsed time. However, it is also possible that the batteryconsumption is estimated based on other data either instead of or inaddition to the received data. In one variation the update of thebattery consumption may be made independently of the received data. Thebase station may for instance measure channel gain updates from otherreference signals, such as the sounding reference signal (SRS) in LTEand use for updating the battery consumption estimation. Based on theseupdated estimations, and thus perhaps based on at least some of thereceived data, the scheme may thus be updated by the uplink schemedetermining unit 24, step 62. If the scheme is updated, the transmissioncontrol unit 30 is then informed in a suitable way.

In both cases, both when there is new data that may or may not cause anupdate of the scheme or if there is no new data, the scheme applicationcontrol unit 32 continues to obtain traffic load data, step 64, andcompare the traffic load with a traffic load threshold, which trafficload data is then especially traffic load having a higher priority thanthe delay-sensitive data.

If the load is above the threshold, for instance if there is higherpriority traffic above the threshold, then the scheme applicationcontrol unit 32 may inform the transmissions control unit 30 to stopissuing grants according to the scheme. This may be done through adirect command. It may also be done indirectly through emptying thebuffer 31 and stopping generation of artificial data and thus throughremoving the low-priority queue. The scheme application control unit 32may also inform the uplink scheme determining unit 24 to stop updatingthe scheme. However, this is not necessarily the case, since it ispossible that the additional granting according to the scheme will beresumed if the traffic load again permits it.

In this way it is possible to allow the mobile station to send datawithout having to request permission in advance, which considerablyshortens the delay and will therefore enhance the user enjoyment ifbeing involved in an on-line game.

The delay problem was solved through proactively scheduling a mobilestation without actual knowledge of the data it wants to transfer. Thiswas in one embodiment done through employing an internal priority queuein order to make the base station presume that there is low prioritytraffic data needed to be transmitted in the uplink. A control loopprovided by the uplink scheme determining unit then monitors thebehaviour of the mobile station statistically to control the amount ofdata and the periodicity of the data that is assumed to arrive from themobile station.

The effect of implementing a special priority queue is that the mobilestation will get extra opportunities to be scheduled when possiblewithout having any impact on performance for other queues. This meansthat:

In a low load situation, when there are free resources in time andfrequency, e.g. the special priority queue or an a-periodic CQI reportrequest will trigger the transmission control unit to issue periodicgrants to the mobile station.

In a higher load situation, the special priority queue and predictivescheduling based a-periodic CQI report will not be scheduled since datafrom normal priority queues of other mobile stations will beprioritized.

The solution according to the embodiments described above provides anumber of further advantages. It will improve the latency situation in alow load scenario in which the radio resources are not fully used. Anexample of a low load cell can be a pico cell. In such a scenario, partsof the radio resources are likely unused. In this case, it may be a goodapproach for a base station to give the unused resource to any mobilestation which may or may not have data to transmit. If the number ofmobile stations is small, there are many unused resources and resourcescould be granted to a mobile station continuously.

As mentioned above, the sending of the uplink transmission grantstriggered by predictive scheduling may increase the power consumption ofthe mobile station. Therefore, in order to save energy resources in themobile station, it is proposed to switch the predictive schedulingfunctionality ON and OFF based on feedback information sent from themobile station to the uplink traffic control device 21.

Embodiments describing how the predictive scheduling can be switched onand off depending on information received from the mobile station willnow be described with reference to FIGS. 7, 8 and 9. With reference toFIGS. 7-9, the method begins in step 44 with the base station 12providing uplink transmission grants with a certain periodicityaccording to an uplink transmission scheme. In the scenario shown inFIG. 8 the decision to apply predictive scheduling was triggered uponreceipt of a message from the mobile station 20, the message including abuffer status report indicating a zero buffer size. (see leftmost arrowin FIGS. 8 and 9 indicating the start of the predictive scheduling).After a while, in step 70, the base station 12 starts to receivemessages indicating an empty mobile station buffer, i.e. BSR=0. Afterreceiving a number of consecutive messages indicating an empty mobilestation buffer it is in step 72 determined to stop applying predictivescheduling to the mobile station 20. In the scenario shown in FIG. 8 thedecision to stop applying predictive scheduling was triggered uponreceipt of the fourth consecutive message comprising only paddingtransmissions and buffer status reports that indicate that the mobilestation buffer is empty. This is however merely an example and thisnumber could be set arbitrarily or depending on circumstances. Aplurality of received consecutive messages indicating an empty mobilestation buffer provides an indication that the mobile station will notbe sending uplink messages comprising useful information in the nearfuture, whereby the predictive scheduling is stopped. It should also bementioned that the decision to stop applying predictive scheduling canbe based on e.g. obtained traffic load data as described with referenceto FIG. 6, or unsuitable channel quality metrics.

After the predictive scheduling has been switched off, the mobilestation operates in ordinary mode for a period of time, during which themobile station is in discontinuous reception (DRX) inactivity mode. DRXis a mechanism that is specified to save power in a mobile station. Itallows the station to turn off its receiver and transmitter according topredefined rules while maintaining a connection to the base station.After a further period of time in DRX inactivity mode, the mobilestation enters DRX sleep mode. The mobile station is thereafter woken upby a pending scheduling request SR (see FIG. 8). The left arrow markedas PING indicates the arrival of PING data in the buffer of the mobilestation. The base station 12 replies by sending a transmission grant tothe mobile station scheduling the requested transmission.

A while after the mobile station has finished transmitting data, thebase station receives a message from the mobile station comprising dataand information that the mobile station buffer is empty (together with aPING) in step 74. This triggers the base station 12 to restart thepredictive scheduling and the method to return to step 44 according toalternative “Yes”. Even though the message received from the mobilestation indicates an empty mobile station buffer, the receipt of themessage indicates that the mobile station may have more data to transmitin a near future, whereby predictive scheduling is determined torestart. The right arrow marked as PING indicates decoded PING datatransmitted from the base station to e.g. a core network. It should bementioned that the decision to apply or restart predictive schedulingaccording to this method also could be based on any other of thepreviously mentioned reasons, such as an obtained service type indicatoror depending on channel quality metrics.

If, in step 74, no information that triggers predictive scheduling isreceived, the method proceeds to step 76 according to alternative “No”.In step 76, which will be further described with reference to FIG. 9, itis checked whether a Packet Inter Arrival Time, IAT, minus a margin, M,has expired or not. If it has expired this triggers the uplink trafficcontrol device 21 to restart the predictive scheduling and the method toreturn to step 44 according to alternative “Yes”. If it has not expiredthe method returns to step 74 according to alternative “No”.

The decision to restart predictive scheduling based on the predictednext packet arrival time can be accomplished by training the packetInter Arrival Time (IAT) statistics in the network. To ensure predictivescheduling starts earlier than the packet arrival time, a small margin,M, is subtracted from IAT when predicting the next packet arrival timeas shown in FIG. 6. IAT is trained from statistics from previoustransmissions and may be defined as the average time between receipt ofBSR/SR/data that indicates a non-empty mobile station buffer to the timeof receipt of a subsequent BSR/SR/data that indicates a non-empty mobilestation buffer.

IAT may more specifically taken as the average time between T1 and T2;where T1 is the time when a first PING packet is received in the basestation minus 4 ms. 4 ms is the time it takes for the mobile station toreceive the grant until the time the PING is encoded and transmittedover the air. The time of 4 ms is however specific to 3GPP LTE. In caseof retransmissions, the retransmission delay shall be taken intoaccount. That is nrofReTx (number of retransmissions) times RTT (RoundTrip Time). T1 is then the time when a first PING packet is received inthe base station minus 4 ms minus nrofReTx multiplied by RTT. T2 is thetime when the base station receives a non-zero BSR or a schedulingrequest.

The margin, M, can be of a predetermined constant value, e.g. xmilliseconds, or M could be dependent on the value of IAT, e.g. xpercentages of the value of IAT. With this proposal, the predictivescheduling request is based on the IAT which enables restart of thepredictive scheduling without the mobile station sending a schedulingrequest. The scheduling delay is thus further reduced. It should bementioned that the decision to restart predictive scheduling based onIAT may be made regardless of the reason for previously stoppingperforming predictive scheduling.

Furthermore, since the predictive scheduling in this embodiment isrestarted when a packet is predicted to arrive the predictive schedulingbased uplink transmission can be made more efficient and the mobilestation battery can be saved. This approach is well suited forapplications with predictable traffic pattern.

Furthermore, to further save energy for the mobile station, a predictivescheduling request may be aligned with DRX ON. By aligning DRX ONduration with a predictive scheduling request, energy can be furthersaved. When in DRX silent mode, the mobile station basically switchesoff the receiver and transmitter. By aligning a predictive schedulingrequest with the DRX pattern, i.e., by sending a predictive schedulinggrant at DRX ON duration, the mobile station receiver can be switchedoff and the battery can be further saved. One example of DRXconfiguration is to set the inactivity timer to 1 ms, ON duration to 1ms and DRX cycle to 2 ms.

According an embodiment, the periodicity of the predictive scheduling isbased on average channel quality for the mobile station. Examples ofchannel quality metrics are path loss (PL) and gain to interference plusnoise ratio (GINR). FIG. 10 illustrates a diagram showing an example ofhow the energy consumption varies with path loss for a mobile stationbased on a reference traffic model. Five different functions are shownin the diagram. The uppermost function 100 is indicated with circles andshows how the power consumption for uplink transmissions for the mobilestation varies with path loss when predictive scheduling is applied withan interval between consecutive uplink transmission grants being 1millisecond. The second function 102 from the top of the diagram,indicated with vertical lines, shows an interval between consecutiveuplink transmission grants being 2 milliseconds. The third function 104from the top of the diagram, indicated with squares, shows an intervalbetween consecutive uplink transmission grants being 5 milliseconds. Thefourth function 106 from the top of the diagram, indicated with crosses,shows an interval between consecutive uplink transmission grants being10 milliseconds. The fifth function 108 from the top of the diagram,indicated with triangles, shows an interval between consecutive uplinktransmission grants being 20 milliseconds. Each of these five functionsshows the scenario when the mobile station transmits a ping packet of100 bytes. Further a sixth function 110 is shown in the diagram andindicated with dots. This function shows how the power consumption forthe mobile station varies with path loss when the mobile station istransmitting data with a size of 1500 bytes. Also shown in the figure isa reference power consumption level 112, which is the mobile stationpower consumption when transmitting a packet having a size of 1500 bytesat a cell edge and experiencing a path loss of 115 dB. This referencepower consumption level 112 is thus in this embodiment equal to thevalue of the mobile station power consumption when the sixth function112 experiences a path loss of 115 dB, i.e. approximately equal to 42dBm. The reason for setting it to 115 dB is that in this embodiment amobile station becomes power limited at a path loss of 115 dB, whichmeans that more transmissions are needed and thus higher powerconsumption at higher path loss.

As can be seen in the FIG. 10, in order for the mobile station to fallshort of the reference power consumption level when transmitting pingpackets of 100 bytes, the uplink traffic control device may providepredictive scheduling at (approximately) a periodicity of 1 millisecondswhen the path loss is below 90 dB, 2 milliseconds when the path loss isbelow 108 dB, 5 milliseconds when the path loss is below 115 dB, 10milliseconds when the path loss is below 121 dB and finally 20milliseconds when the path loss is below 126 dB. These figures will ofcourse be different in case e.g. the data sizes of the transmitting pingpackets are changed.

By measuring the path loss and adapting the periodicity of the uplinktransmission scheme when the path loss for the mobile station exceedsthreshold values, a trade-off between scheduling latency and powerconsumption is achieved. According to the example described above andshown in FIG. 10 the periodicity of the predictive scheduling is set tochange: from 1 ms to 2 ms when a path loss exceeding 90 dB (but beingbelow 108 dB) is detected, from 2 ms to 5 ms when a path loss exceeding108 dB (below 115) is detected, from 5 ms to 10 ms when a path lossexceeding 115 dB (below 126) is detected, and from 10 ms to 20 ms when apath loss exceeding 126 dB is detected. Correspondingly the periodicityof the predictive scheduling is set to change from 20 ms to 10 ms when apath loss falling short of 115 dB (but being above 108) is detected,etc.

By changing the uplink transmission scheme depending on detected pathloss by e.g. modifying the periodicity of the predictive schedulinggrants, the scheduling latency is decreased while also limiting thepower consumption for a mobile station experiencing a high path loss,e.g. for a mobile station located in a cell edge. With this adaptivepredictive scheduling periodicity scheme, the tradeoff betweenscheduling delay and mobile energy consumption is obtained. A mobilestation with good channel quality metrics will be scheduled with shorterperiodicity and thus shorter scheduling delay; a user with poor channelquality will be scheduled with longer periodicity which indicates longerscheduling delay. From the energy perspective, a mobile with goodchannel quality will be scheduled with more pre-scheduling transmissionscomparing to mobile stations with bad channel quality. However, a mobilestation that has a higher channel quality will need fewer transmissionsand a lower power consumption to transmit the same amount of data as amobile station having a lower channel quality. Thus, the uplinktransmission energy balance between mobile stations experiencing goodand bad channel quality can be obtained. Thus, not only latency but alsobattery consumption is optimized to maintain the best performance.Furthermore, a mobile station with a high average channel quality istypically located in the center of a cell, thus generating less intercell interference, whereas a mobile station with lower channel qualityis typically located in a cell edge and thus generating more inter cellinterference. This allows more uplink transmissions in the cell centerbut fewer transmissions at the cell edge, which can thus lower the intercell interference.

In the example given above the uplink traffic control device wasprovided in the first base station. It should be realized that it may beprovided in another network node instead, which communicates with thefirst base station.

Furthermore, a lot of the above described functionality may be omitted.It is for instance possible that the battery consumption is notestimated or that higher priority traffic is not considered. It is alsopossible to omit the considering of historical or statistical data aswell as the use of the buffer with artificial data.

The uplink scheme determining module of the uplink traffic controldevice may be provided as a dedicated circuit such as a digital signalprocessor (DSP) or an Application Specific Integrated Circuit (ASIC). Asan alternative it may be provided in the form of a processor withassociated program memory including computer program code for performingthe functionality of its units.

This computer program may also be a computer program product, forinstance in the form of a computer readable storage medium or datacarrier, like a CD ROM disc or a memory stick, carrying such a computerprogram with the computer program code, which will implement thefunction of the above-described module when being loaded into an uplinktraffic control device. One such computer program product in the form ofa CD ROM disc 68 with the above-mentioned computer program code 69 isschematically shown in FIG. 11.

What is claimed is:
 1. A method in a network node for controllingpredictive scheduling in a wireless communication network between a basestation applying the predictive scheduling and a mobile station,according to an uplink transmission scheme, wherein the uplinktransmission scheme schedules a plurality of uplink transmission grants,based on the predictive scheduling, to be transmitted from the basestation to the mobile station without having received a schedulingrequest from the mobile station requesting the uplink transmissiongrants, the method comprising: determining a discontinuous reception(DRX) configuration for the mobile station; and aligning the uplinktransmission scheme of the predictive scheduling with the DRXconfiguration by: sending predictively scheduled uplink transmissiongrants from the base station to the mobile station during DRX ON state;and refraining from sending the predictively scheduled uplinktransmission grants from the base station to the mobile station duringDRX OFF state.
 2. The method according to claim 1, wherein a duration ofthe DRX ON state is 1 ms.
 3. The method according to claim 1, wherein aDRX cycle is 2 ms and a duration of the DRX ON state is 1 ms.
 4. Themethod according to claim 1 further comprising determining a periodicityof the predictively scheduled uplink transmission grants based onchannel quality for the mobile station.
 5. The method according to claim1, further comprising applying the predictive scheduling based on bufferstatus of the mobile station.
 6. A network node for controllingpredictive scheduling in a wireless communication network between a basestation and a mobile station, the network node configured to initiatepredictive scheduling for the mobile station according to an uplinktransmission scheme, wherein the uplink transmission scheme schedules aplurality of uplink transmission grants, based on the predictivescheduling, to be transmitted from the base station to the mobilestation without having received a scheduling request from the mobilestation requesting the uplink transmission grants, the network nodecomprising: a processor; and a memory containing instructions which,when executed by the processor, cause the network node to performoperations to: determine a discontinuous reception (DRX) configurationfor the mobile station; and align the uplink transmission scheme of thepredictive scheduling with the DRX configuration by performingoperations to: send predictively scheduled uplink transmission grantsfrom the base station to the mobile station during DRX ON state; andrefrain from sending the predictively scheduled uplink transmissiongrants from the base station to the mobile station during DRX OFF state.7. The network node according to claim 6, wherein a duration of the DRXON state is 1 ms.
 8. The network node according to claim 6, wherein aDRX cycle is 2 ms and a duration of the DRX ON state is 1 ms.
 9. Thenetwork node according to claim 6 further performing operations todetermine a periodicity of the predictively scheduled uplinktransmission grants based on channel quality for the mobile station. 10.The network node according to claim 6, further performing operations toapply the predictive scheduling based on buffer status of the mobilestation.
 11. A non-transitory computer readable storage medium havingstored thereon computer program code which, when executed by aprocessing device of a network node, is capable of causing the networknode to have a base station apply predictive scheduling of uplinktraffic from a mobile station in a wireless communication network,according to an uplink transmission scheme, wherein the uplinktransmission scheme schedules a plurality of uplink transmission grants,based on the predictive scheduling, to be transmitted from the basestation to the mobile station without having received a schedulingrequest from the mobile station requesting the uplink transmissiongrants, by performing operations comprising: determining a discontinuousreception (DRX) configuration for the mobile station; and aligning theuplink transmission scheme of the predictive scheduling with the DRXconfiguration by: sending predictively scheduled uplink transmissiongrants from the base station to the mobile station during DRX ON state;and refraining from sending the predictively scheduled uplinktransmission grants from the base station to the mobile station duringDRX OFF state.
 12. The non-transitory computer readable storage mediumaccording to claim 11, wherein a duration of the DRX ON state is 1 ms.13. The non-transitory computer readable storage medium according toclaim 11, wherein a DRX cycle is 2 ms and a duration of the DRX ON stateis 1 ms.
 14. The non-transitory computer readable storage mediumaccording to claim 11, wherein the computer program code is furthercapable of causing the network node to perform operations comprisingdetermining a periodicity of the predictively scheduled uplinktransmission grants based on channel quality for the mobile station. 15.The non-transitory computer readable storage medium according to claim11, wherein the computer program code is further capable of causing thenetwork node to perform operations comprising applying the predictivescheduling based on buffer status of the mobile station.